WO2012134008A1

WO2012134008A1 - Power amplifier using differential structure

Info

Publication number: WO2012134008A1
Application number: PCT/KR2011/007600
Authority: WO
Inventors: 박종훈; 박창근
Original assignee: 숭실대학교산학협력단
Priority date: 2011-03-28
Filing date: 2011-10-13
Publication date: 2012-10-04
Also published as: US9019013B2; KR101167454B1; US20140232462A1

Abstract

The present invention relates to a power amplifier using a differential structure. The power amplifier using a differential structure of the present invention comprises: a first transistor and a second transistor, each having a first end, each connected to a first power supplying a first voltage, having a same size, and inputted with signals having opposite polarity; a third transistor and a fourth transistor, each having a first end, which are each connected to the first ends of the first transistor and the second transistor; and a fifth transistor having a first end connected to second ends of the third transistor and the fourth transistor, and for controlling the oscillation of the third transistor or the fourth transistor. The power amplifier using a differential structure reduces the drive power needed for a power amplifying stage or enables a greater output by using an assistant transistor. In addition, a switch transistor for controlling the oscillation is configured to connect only with the assistant transistor causing the oscillation, thus realizing the switch transistor in a small size, and reducing the manufacturing cost thereby.

Description

Power Amplifier Using Differential Structure

The present invention relates to a power amplifier using a differential structure, and more particularly, to a power amplifier using a differential structure capable of minimizing the size of a transistor for preventing oscillation.

One of the circuits commonly used in high frequency integrated circuits for wireless communication systems, power amplifiers are used to increase the power of the applied signal. In particular, the differential power amplifier has a strong characteristic against noise in a semiconductor substrate because the signals applied to the basic transistors of the left and right stages have the same magnitude and opposite polarity to amplify the difference between the two signals. There is an advantage that can double the power by using both sides. However, when a large number of transistors are connected for a large output power, a driving power for driving them is required.

1 and 2 is a block diagram showing a power amplifier of a differential structure according to the prior art. The power amplifier according to FIG. 1 is to more effectively amplify the output power, and further supports the amplification of the base transistor in the power amplifier structure including the transistors 10 and 20 (hereinafter referred to as 'base transistors'). , Hereinafter referred to as a "help transistor." The

base transistors

10 and 20 and the

help transistors

30 and 40 share a drain and a source, respectively, and the gates of the

help transistors

30 and 40 are connected to

opposite output ports

50 and 60.

In the power amplifier illustrated in FIG. 1, since the

help transistors

30 and 40 help amplification, the

basic transistors

10 and 20 can produce a larger output even if they are formed in a small size, and thus the driving power required is reduced. There is this. However, when no signal is applied, the

help transistors

30 and 40 operate due to the power supply voltage Vs, causing oscillation.

2 is a view showing another example of the power amplifier presented to solve the problem of the power amplifier according to FIG. The power amplifier shown in FIG. 2 is a transistor (70, hereinafter referred to as a "switch transistor") for additionally controlling oscillation in the power amplifier structure shown in FIG. 1 and a switch transistor 80 having opposite characteristics to the switch transistor 70. Is added. Here, the drain of the switch transistor 70 is connected to the source of the

base transistors

10 and 20 and the source of the

help transistors

30 and 40, respectively, and the source is connected to the ground power source. In addition, the source of the switch transistor 80 is connected to the power source 25 of the same size (Vs) as the power supply voltage, the gate of the switch transistor 70 and the switch transistor 80 is connected to each other to apply a signal for controlling the oscillation do.

In the power amplifier illustrated in FIG. 2, when the control signal applied to the switch transistor 70 is at a low level, since the switch transistor 70 cannot operate, the power amplification stage is disconnected from the ground power supply, whereas the switch transistor 80 ) Is operated so that the power amplification stage and the Vs power supply 25 are connected to each other, and since the current cannot flow because the voltages of the power supply 15 and the power supply 25 are the same, the oscillation of the helper transistor 40 is blocked. . On the contrary, when the control signal applied to the switch transistor 70 is at a high level, the power amplifier stage and the ground power source are connected while the switch transistor 70 is operated to enable the power amplifier stage to amplify. However, the switch transistor 70 has to deal with the current flowing through the

base transistors

10 and 20 and the

help transistors

30 and 40, and the size of the switch transistor 70 must be very large to prevent the amplification factor from being lowered. have.

Accordingly, the present invention is directed to a power amplifier using a differential structure capable of minimizing the size of a transistor for preventing oscillation.

According to an embodiment of the present invention, a power amplifier using a differential structure according to an embodiment of the present invention may have a first end connected to a first power supply for supplying a first voltage, and a signal having the same magnitude and opposite polarity may be input. A third transistor and a fourth transistor having a first end connected to a first transistor and a second transistor, a first end of the first transistor and the second transistor, respectively, and a second of the third transistor and the fourth transistor. A first stage is connected to the stage, and includes a fifth transistor that controls the oscillation of the third transistor or the fourth transistor.

The first transistor and the second transistor may amplify respective signal differences applied, and the third and fourth transistors may assist with amplification by the first and second transistors.

Second terminals of the first transistor, the second transistor, and the fifth transistor may be connected to a second power supply that supplies a second voltage lower than the first voltage.

When the first transistor and the second transistor are turned off, the fifth transistor may be turned off.

A first end is connected to the second end of the third transistor and the second end of the fourth transistor, the first power source and the second end are connected, and the third end and the third end of the fifth transistor are connected. It may further include a sixth transistor.

When the first transistor and the second transistor are turned off, the fifth transistor may be turned off and the sixth transistor may be turned on.

The fifth transistor and the sixth transistor may be transistors having different polarities.

The third terminal of the third transistor may be connected to the first terminal of the second transistor, and the third terminal of the fourth transistor may be connected to the first terminal of the first transistor.

A first inductor connected between the first power source and the first transistor, a second inductor connected between the first power source and the second transistor, and connected between the first inductor and the first end of the first transistor The display device may further include a first output port and a second output port connected between the second inductor and the first terminal of the second transistor.

As described above, according to the power amplifier using the differential structure according to the present invention, by using the help transistor, the required driving power of the power amplifier stage can be reduced or high output can be obtained. In addition, by configuring the switch transistor for controlling the oscillation to be connected only to the help transistor that causes the oscillation, the switch transistor can be implemented in a small size, thereby reducing the manufacturing cost.

1 and 2 is a block diagram showing a power amplifier of a differential structure according to the prior art.

3 is a circuit diagram of a power amplifier using a differential structure according to the first embodiment of the present invention.

4 is a circuit diagram of a power amplifier using a differential structure according to a second embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. . In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

In addition, the expression that voltage is maintained throughout the specification indicates that even if the potential difference between two specific points changes over time, the change is within an allowable range in the design or the cause of the change is due to parasitic components that are ignored in the design practice of those skilled in the art. Include cases by. In addition, since the threshold voltage of a semiconductor device (transistor, diode, etc.) is very low compared to the discharge voltage, the threshold voltage is regarded as 0V and approximated.

3 is a circuit diagram of a power amplifier using a differential structure according to the first embodiment of the present invention. The power amplifier using the differential structure according to the first embodiment of the present invention shown in FIG. 3 includes

inductors

201 and 202 and

transistors

210, 220, 230, 240 and 250. The power amplifier using the differential structure according to the embodiment of the present invention amplifies a voltage difference between two input signals applied to both ends of the

basic transistors

210 and 220.

Signals having the same magnitude and opposite polarities are applied to the

transistors

210 and 220 corresponding to the basic transistor, respectively, and amplify the output voltage corresponding to the difference between the two signals. In addition, the

transistors

230 and 240 corresponding to the help transistor serve to amplify the output of the power amplifier illustrated in FIG. 3. In addition, the transistor 250 corresponding to the switch transistor controls the operation of the

help transistors

230 and 240 to prevent oscillation of the power amplifier shown in FIG. 3.

In FIG. 3, the

transistors

210, 220, 230, 240, 250 are illustrated as n-channel field effect transistors, in particular, n-channel metal oxide semiconductor (NMOS) transistors. The body diode may be formed in the direction from the source to the drain.

And other transistors having similar functions in place of the NMOS transistors may be used as these

transistors

210, 220, 230, 240, 250. In addition, in FIG. 3, the

transistors

210, 220, 230, 240, and 250 are shown as one transistor, respectively, but the

transistors

210, 220, 230, 240, and 250 may each be formed of a plurality of transistors connected in parallel. .

Hereinafter, the connection relationship of the power amplifier using the differential structure according to the first embodiment of the present invention shown in FIG. 3 will be described in detail.

As shown in FIG. 3, the first stages of the inductor 201 and the inductor 202 are connected to a power supply 205 that supplies a power amplifier power supply voltage Vs. The second end of the inductor 201 is connected to the drains of the

transistors

210 and 230, and the second end of the inductor 202 is connected to the drains of the

transistors

220 and 240. Here,

output ports

221 and 222 are provided between the second end of the inductor 201 and the drain of the transistor 210, and between the second end of the inductor 202 and the drain of the transistor 220. do.

Sources of the

transistors

210 and 220 are connected to a ground power source, respectively, and signals for controlling turn-on / turn-off operations of the

transistors

210 and 220 are input to the gates. Here, due to the characteristics of the differential structure power amplifier, signals having opposite polarities are input to the gates of the

transistors

210 and 220 corresponding to the basic transistors, and the turn on / off operations of the

transistors

210 and 220 are opposite to each other. .

The gate of transistor 230 is connected to output port 222 and the gate of transistor 240 is connected to output port 221. In addition, the sources of the

transistors

230 and 240 are respectively connected to the drain of the transistor 250, and the source of the transistor 250 is connected to the ground power source. The control signal for controlling the oscillation of the power amplifier is input to the gate of the transistor 250.

Hereinafter, the operation of the power amplifier using the differential structure according to the first embodiment of the present invention will be described. Since the opposite signals are applied to the

transistors

210 and 230 and the

transistors

220 and 240, the

transistors

220 and 240 are turned off when the

transistors

210 and 230 are turned on, and vice versa. same. When any one of the

transistors

210 and 220 is turned on, a high level signal is input to the transistor 250 to maintain the turned on state.

For convenience of description, it is assumed that the

transistors

210 and 230 are turned on, and the

transistors

220 and 240 are turned off, and the transistor 210 is turned off. In this case, since the transistor 230 is turned on, the current drawn from the power supply 205 is transferred to the transistor 230, and an oscillation phenomenon may occur in which the transistor 230 operates. The oscillation phenomenon is a phenomenon in which an unintended signal is output even though there is no input signal. According to the exemplary embodiment of the present invention, the oscillation by the transistor 230 may be prevented by providing the transistor 250.

That is, according to the first embodiment of the present invention, when the transistor 210 is turned off as described above, since both the transistor 210 and the transistor 220 are turned off, the gate of the transistor 250 has a transistor ( A low level signal is input which causes 250 to be turned off. Therefore, when the transistor 250 is turned off, since the connection between the transistor 230 and the ground power supply is cut off, the transistor 230 is not operated to prevent the power amplifier from oscillating.

On the contrary, even when the

transistors

210 and 230 are turned off and the transistors 220 are turned off while the

transistors

220 and 240 are turned on, the transistor 250 is turned off, The connection is broken to prevent the differential amplifier from oscillating.

As described above, according to the first embodiment of the present invention, as the transistor 250 for controlling the oscillation is connected to the

transistors

230 and 240, the transistor 230 may be turned off even when the

basic transistors

210 and 220 are both turned off. Alternatively, the problem that the transistor 240 causes oscillation can be solved. As described above, according to the first embodiment of the present invention, since the transistor 250 blocks oscillation by the

transistors

230 and 240, it is possible to prevent loss of power due to oscillation.

In addition, according to the first embodiment of the present invention, the transistor 250 is connected only to the

transistors

230 and 240 and not to the

transistors

210 and 220. Accordingly, since the transistor 250 only needs to cover the current flowing through the

transistors

230 and 240 in the operation of the differential amplifier according to the first embodiment of the present invention, the transistor 250 is compared with the conventional power amplifier shown in FIG. It is economical in that the size of can be reduced to 50% or less.

4 is a circuit diagram of a power amplifier using a differential structure according to a second embodiment of the present invention. The power amplifier using the differential structure according to the second embodiment of the present invention shown in FIG. 4 includes

inductors

201 and 202 and

transistors

210, 220, 230, 240, 250, and 260. The power amplifier according to the second embodiment of the present invention shown in FIG. 4 further includes a transistor 260 as compared with the first embodiment of the present invention, and has the

same reference numerals

201, 202, 205, and 210. , 220, 230, 240, and 250 have substantially the same function and connection relationship, and thus overlapping descriptions will be omitted and differences from the first embodiment of the present invention will be described.

First, the gate of the transistor 260 is connected to the gate of the transistor 250, and the same oscillation control signal is input. The transistor 260 is a transistor having a polarity opposite to that of the transistor 250. In the second embodiment of the present invention, since the transistor 250 is illustrated as an NMOS transistor, the transistor 260 is a p-channel metal oxide semiconductor (PMOS). Transistor. As shown in FIG. 4, since the gate of the transistor 250 and the gate of the transistor 260 are connected to each other, the transistor 250 and the transistor 260 perform opposite operations according to one input signal.

The drain of the transistor 250 and the drain of the transistor 260 are both connected to the transistor 230 and the transistor 240. That is, the source of the transistor 230 and the source of the transistor 240 are connected to each other through a wire, some point of the wire is connected to the drain of the transistor 250, and another part of the wire is connected to the transistor 260 It is connected to the drain of. In addition, the source of the transistor 250 is connected to the ground power supply, while the source of the transistor 260 is connected to the power supply 215 having the same voltage as the power supply voltage Vs.

Hereinafter, the operation of the power amplifier using the differential structure according to the second embodiment of the present invention will be described.

As described above, when any one of the

transistors

210 and 220 is turned on, the transistor 250 remains turned on, and since the transistor 260 operates opposite to the transistor 250, the transistor 260 is It is turned off.

Like the first embodiment of the present invention, for convenience of description, it is assumed that the

transistors

210 and 230 are turned on, and the

transistors

220 and 240 are turned off, and the transistor 210 is turned off. According to the second embodiment of the present invention, when the transistor 210 is turned off, since both the transistor 210 and the transistor 220 are turned off, a low level signal is input to the gate of the transistor 250 so that the transistor 250 is turned off and transistor 260 is turned on.

Therefore, when the transistor 250 is turned off and the transistor 260 is turned on, the voltage across the transistor 230 is the same as Vs, so that the voltage drop cannot be made. Accordingly, the transistor 230 may not operate to prevent the differential amplifier from oscillating.

In contrast, when the

transistors

210 and 230 are turned off and the transistors 220 are turned off while the

transistors

220 and 240 are turned on, the transistor 250 is turned off and the transistor 260 is turned on. At this time as well, since the voltage across the transistor 240 is the same as Vs, the transistor 230 cannot operate and prevents the differential amplifier from oscillating.

As described above, according to the power amplifier using the differential structure according to the embodiment of the present invention, by using the

help transistors

230 and 240, the required driving power of the power amplifier stage can be reduced or a large output can be produced.

In addition, since the

transistors

250 and 260 for controlling the oscillation are configured to be connected only to the

help transistors

230 and 240 which cause the oscillation, the

switch transistors

250 and 260 can be realized with a small size, which leads to a manufacturing cost. Economic savings can be achieved.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims

A first transistor and a second transistor having a first end connected to a first power supply for supplying a first voltage and having a signal having the same magnitude and opposite polarity, respectively;

A third transistor and a fourth transistor, each having a first end connected to a first end of the first transistor and the second transistor, and

The first amplifier is connected to the second terminal of the third transistor and the fourth transistor, the power amplifier using a differential structure including a fifth transistor for controlling the oscillation of the third transistor or the fourth transistor.
The method of claim 1,

The first transistor and the second transistor amplify the respective signal difference is applied,

The third and fourth transistors are power amplifiers using a differential structure to assist the amplification by the first and second transistors.
The method of claim 2,

And a second terminal of the first transistor, the second transistor, and the fifth transistor is connected to a second power supply for supplying a second voltage lower than the first voltage.
The method of claim 3,

And the fifth transistor is turned off when the first transistor and the second transistor are turned off.
The method of claim 3,

A first end is connected to the second end of the third transistor and the second end of the fourth transistor, the first power source and the second end are connected, and the third end and the third end of the fifth transistor are connected. A power amplifier using a differential structure further comprising a sixth transistor.
The method of claim 5,

And the fifth transistor is turned off and the sixth transistor is turned on when the first and second transistors are turned off.
The method of claim 6,

And the fifth transistor and the sixth transistor are transistors having different polarities.
The method of claim 1,

And a third end of the third transistor is connected to a first end of the second transistor, and a third end of the fourth transistor is connected to a first end of the first transistor.
The method of claim 1,

A first inductor connected between the first power supply and the first transistor,

A second inductor connected between the first power supply and the second transistor,

A first output port connected between the first inductor and the first terminal of the first transistor, and

And a second output port coupled between the second inductor and the first end of the second transistor.